The present invention relates to an apparatus for transferring sheet materials such for example as printed-circuit boards, sheets of glass, or raw films.
Transfer apparatus known as sheet material lifters are used for elevating a stack or pile of sheet materials up to a vacuum chuck and enabling the latter to pick up the uppermost sheet from the stack thus lifted. The position of the top face of the sheet pile is optically detected to determine the positional difference between the top sheet face and the vacuum chuck, so that a table with the sheets piled up thereon can be lifted to bring the uppermost sheet of the stack against the vacuum chuck. When all of the stacked sheets are removed from the table, the table is lowered to its lowermost position, in which another stack of sheets is placed on the table. During this stacking operation, no sheet can be picked up from the table.
Another prior transfer apparatus comprises a rack cassette for housing sheet materials in bins or compartments therein. The rack cassette is driven in a pickup station to move the bins or compartments successvely into alignment with a pickup position, in which the sheet is pushed or drawn out of the corresponding bin. After all of the bins have been emptied, the rack cassette is required to be replaced with another rack cassette with sheet materials housed therein, during which time the process of picking up sheet materials must be suspended. The foregoing prior arrangements are disadvantageous in that they allow sheet materials to be picked up only intermittently, but not continuously.
According to still another conventional apparatus, sheet materials are placed horizontally on a belt conveyor for being transferred thereby. This transfer apparatus however takes up quite a wide space.